Nek5000  is a Fortran and MPI simulation code for the simulation of incompressible flows in complex geometries. The code is used to study the fluid-dynamics in fission nuclear reactors and improve their design in order to avoid accidents. The numerical discretisation is based on the spectral-element method, which combines the high-order accuracy from spectral methods with the geometric flexibility of finite-element methods. Nek5000 is maintained at Argonne National Laboratories (USA) by Paul Fischer, and is used at many Universities in Europe, including e.g. KTH Stockholm, and ETH Zürich.nek5000imagediff
The KTH group has extensive collaborations with the Nek5000 development team. Nek5000 was designed to be a code toemploy large-scale parallelism. The Nek5000 code has a long history of HPC development, including  a 1999 Gordon Bell Award, and successful scaling to 290,000 processors on the Julich BG/P. The computational cost is dominated by matrix products that are well suited to exascale architectures.  Nek5000 is part of the application suite of the CRESTA European exascale project and it has used as benchmark in several exascale benchmarks. Differently from CRESTA project, where the focus of the work are on algorithmic improvements (implementation of error estimators and adaptive algorithms), EPiGRAM will work on purely software issues, such as the development of new highly scalable communication kernels to enable Nek5000 exascale performance.

A. Peplinski, P. Schlatter, and D. S. Henningson. Global stability and optimal perturbation for a jet in cross-flow. Eur. J. Mech. B/Fluids, 49:438–447, 2015